Electro-acoustic device



NOV. 13, 1934. R. D. PARRY 1,980,957

ELECTROAGOUSTIC DEVI CE Original Fil ed Feb. 27, 1929 Inventor: Robert D. Parrg,

His Attorneu.

Patented Nov. 13, 1934 UNITED STATES PATENT OFFHCE ELECTRO -ACOUSTIC DEVICE poration of New York Application February 27, 1929, Serial No. 343,102.

Renewed May 20, 1933. In Great Britain February 27, 1928 17 Claims.

My invention relates to electro-acoustic devices for the interconversion of mechanical vibrations and electric oscillations, for example, to loud-speakers which, as is well known in the art,

' can be adapted to operate as transmitters. The invention is primarily applicable to the largediaphragm type of hornless loudspeakers.

According to the invention, the diaphragm of an electro-acoustic device comprises two or more portions arranged to provide a substantiallycontinuous surface, and eachportion is adapted to be positively actuated. Whereas these portions might, theoretically, be arranged side-byside, it is preferable to split a diaphragm (for example, a disc. or' cone-type diaphragm) into two outer annular portions and an inner central portion, operating means being connected to each portion.

A further feature according to the invention consists in a diaphragm, comprising two outer annular portions and an inner central portion of materially different sizes, in which each portion of the diaphragm is flexibly supported or otherwise adapted to vibrate substantially as a whole. Preferably, the diaphragm is shaped in a manner to take the form of a dish, a cap of a sphere, a conical surface or a truncated cone surface, which, for the purpose of this specification, are all deemed to be included within the term conetype. Such a cone-type diaphragm when adapted according to the invention will be very flexibly supported or otherwise guided in any suitable manner but, in addition, it may include a flexible co-axial circular connection located preferably towards its smaller end.

1 A preferred arrangement according to the invention involves a cone-type loud-speaker or like device having two co-axial circular gaps dividing its diaphragm into three different-sized portions, and annular operating means connected to the three portions of the diaphragm.

' By splitting up the diaphragm into three unequal portions as described above, one portion can be arranged to operate in a manner to produce the high frequency vibrations, and the other portions to produce the low frequency vibrations. For example, in the case of a cone-type diaphragm of about 6" diameter at its larger or open end, thesmaller portion may have a diameter of about Such an arrangement, therefore, will avoid the objection to which many known types of hornless loud-speakers are open, namely, that they fail adequately to produce the low notes.

The operating means above referred to may take any known form, such, for instance, as a reed or reeds rockable between the poles of a magnetic structure in accordance with the oscillations of current supplied to a coil associated therewith or with the magnetic structure. Other known types of armature devices may, however, be used. When the operating means is to be of annular form it may include an annular coil or coils (or a closed ring or rings of conducting material) located in a magnetic field of the device and connected to the three portions of the diaphragm. Alternatively, it may be in the form of an annular member or members of magnetic material located in a magnetic field which is substantially constant and associated with the fluctuating field due to a suitably-arranged coil or coils fed with oscillating current.

A further feature according to the invention involves the use of a-magnetic structure which provides three annular concentric air-gaps, each airgap being associated with an annular operating means connected, respectively, to the three portions of the diaphragm.

Whereas particular reference has been made above to splitting up the diaphragm into three portions, acoustic advantages may accrue from splitting up the diaphragm into only two or even a greater number of portions, preferably of different sizes, and arranging for each portion to be positively actuated; though naturally such an arrangement would increase the manufacturing cost. The invention is not limited to a diaphragm or to the use of a diaphragmsplit only into three portions.

A further feature according to the invention relates to the use of a magnetic structure which provides two or more annular concentric air-gaps, and involves an arrangement by which the alternate pole-pieces, between which the air-gaps are located, are of opposite polarity. Thus, in the case of two annular air-gaps, the central core may terminate in a north pole, the middle annular core in a south pole, and the outer shell in another north pole. If an exciting winding is utilized, the turns around the central core will be in a direction opposite to that of the turns around said middle annular core.

One arrangement of loud-speaker in accordance with the invention is illustrated for the sake of example in Fig. 1 of the accompanying drawing as applied to a loud-speaker embodying the conetype diaphragm actuated by a moving coil. In, Fig. 2 of the drawing is shown one modification of the voice coil circuit.

The cone-type diaphragm 1 is divided into 3&1

three sections 2, 3 and 4, the surfaces of which are contiguous. The outer edge of the outer portion 2 is flexibly supported at 5 to a casing shown diagrammatically at 6. The outer edge of the middle portion 3 is flexibly supported at '7 to the inner edge of the outer portion 2 and portion 4 is in turn supported at 8 by the portion 3. Each portion of the diaphragm is positively actuated, the outer portion 2 by means of an annular coil 9, the middle portion 3 by coil 10, and the inner portion 4 by means of similar annular coil 11. Coils 9, 10 and 11 are located in a known manner in magnetic fields which, inthe arrangement illustrated, are produced by a composite magnet structure 12 providing three separate annular airgaps l3, l4 and 15 in which the coils 9,10 and 11' are respectively located. Cooperating pole pieces which provide the concentric air gaps are of opposite polarity and in order to provide suitable tion opposite to that of the turns of coil 17 and.

the turns of coil 18 should be in the same direction as those of coil 16.

The operating coils for the several portions of the diaphragm may be connected in series with one another, as indicated, for example, in Fig. 2 of the drawing wherein the voice coils 9, l0 and 11 are shown as supplied in series from a source of sound current through the leads 20 and 21.

By constructing a cone-type diaphragm in this manner the actuating forces applied to the diaphragm are more evenly distributed and the tendency of the cone to collapse when the pull is towards the apex thereof is very considerably reduced.

, What I claim as new and desire to secure by Lettersv Patent of the United States is:

l. A loud-speaker or like device including a cone-type diaphragm comprising a plurality of concentric portions arranged to provide a substantially continuous surface and separate means for positively actuating each portion, one of said portions being arranged to produce high frequency vibrations, the others of said portions being arranged'respectively to produce successively lower frequency vibrations.

2.,A loud-speaker or like device including a cone-type diaphragm which is divided to form an outer annular portionand an inner central portion and operating means connected to both portions, said inner central portion and said outer annular portions being arranged respectively to produce relatively high frequency and relatively low frequency vibrations.

3. An electroresponsive device including a sound diaphragm comprising a plurality of concentric portions, flexible connections between said portions, and means to individually actuate each portion.

4. An electroresponsive device including a sound diaphragm comprising a plurality of concentric portions arranged to form a substantially continuous surface, flexible connections between said portions, and means arranged to individually actuate each portion.

5. A loud-speaker or like device including a magnetic structure providing a plurality of annular concentric air-gaps and a cone-type diaphragm divided into co-axial portions, each portion carrying an annular operating means located in one of the air-gaps, one of said portions being arranged to produce high frequency vibrations,

, the others of said portions being arranged respectively to produce successively lower frequency vibrations.

6. A diaphragm made up of a central rigid zone, a larger rigid zone and connection between the zones made of less rigid material than that of the zones.

'7. In a loud speaker of the type having a large diaphragm freely exposed to non-confined air, a conically shaped diaphragm, divided up into a plurality of circular bands, said bands being connected to each other through bands of flexibly resistant material.

8. A loud speaker or like device including a vibratile element comprising a plurality of portions connected in series by compliant coupling means to provide a substantially continuous surface, said portions being arranged to vibrate at different frequencies, and means to actuate each portion individually.

' 9. A loud speaker or like device including a vibratile element comprising two portions connected at their adjacent edges by compliant coupling means, and individual operating means connected each to a different one of saidportions, said portions being arranged respectively to vibrate at relatively high frequency and at relatively low frequency.

10. An electroresponsive acoustic device including a vibratile element comprising a plurality of portions, compliant coupling means between contiguous portions, and means to actuate each portion individually,

11. An electroresponsive acoustic device including a vibratile element comprising a plurality ofportions arranged to form a substantially continuous surface, compliant coupling means between contiguous portions, and means arranged to actuate each portion individually,

12. An electroresponsive acoustic device including a vibratile structure, a plurality of, driving means for actuating said structure, and compliant coupling means between different p'ortions of said vibratile structure whereby one of. said driving means actuates said structure independently of another of said driving means.

13. An electrodynamic loud speaker including a vibratile structure, a plurality of voice. coils for actuating said structure, and compliant coupling means between different portions of said vibratile.v structure whereby one of said voice coils actuates. said structure independently of another of said" voice coils.

14. An electroresponsive acoustic device in cluding a vibratile structure, a plurality of drive ing means for actuating said structure, and compliant coupling means between different portions of said vibratile structure, whereby one of said driving means actuates said structure independently of another of said driving means, one por-- tion of said vibratile structure being responsive to an audio frequency higher than the frequency at which another portion of said structure is responsive.

15. An electrodynamic loud speaker including a vibratile structure, a plurality of voice coils for actuating said structure, said voice coils beingv connected in series with each other, and compli ant coupling means between different portions of said vibratile structure whereby one of said voice coils actuates said structure independently of another of said voice coils.

15. A loud speaker including a vibratile structure comprising a plurality of portions connected together by compliant coupling means, and in-: dividual driving means for each portion, the d-iftion, each or said driving means being adapted to drive its associated portion 0! the vibratile structure directly and to drive the other portions of the vibratile structure indirectly through the compliant coupling means.

R. D. PARRY. 

